This invention relates generally to silicon-germanium hydrides and silicon hydride analogs. More particularly, it relates to the synthesis of silicon-germanium hydrides having the molecular formula (H3Ge)4-xSiHx, wherein x=0, 1, 2 or 3 and silicon hydride analogs thereof.
Synthesis and development of electronic and optical materials as well as devices based on the Si—Ge and related group IV alloy semiconductor systems, such as Si—Ge—C and Si—Ge—Sn, is currently of interest due to the potentially useful electronic and optical properties of these systems. Commercial fabrication of such systems traditionally has been achieved via chemical vapor deposition (CVD) of disilane (SiH3)2 and digermane (GeH3)2. However, the development of new and useful materials based on these systems with device quality morphological and structural properties requires new low temperature growth methods. Trisilane, (H3Si)2SiH2, is currently used for commercial growth of strained Si channel devices on Si—Ge buffered silicon. A major advantage of trisilane relative to traditional Si hydrides is its higher reactivity, allowing low temperature growth conditions compatible with development of strained Si channels. Previously reported methods for synthesizing trisilane, however, have significant drawbacks. They are based on electric silent discharge of lower Si-hydrides, which typically produce mixtures of materials at low yields. To isolate the trisilane product in pure form, complicated separation and purification procedures need to be employed.
Previous reports discuss the potential synthesis of tetragermylsilane, Si(GeH3)4. W. Dutton and M. Onyszchuk, Inorganic Chemistry volume 7, number 9, 1968. To the best of our knowledge, however, no definitive proof of its existence as a pure product possessing the correct stoichiometry has been provided thus far. The previously reported NMR data revealed a mixture of products and the reported elemental analysis corresponding to Si(GeH3)4 was incorrect. Furthermore, the synthetic method described is unsuitable for producing the compound for commercial applications such as for use as a CVD source.
L. Lobreyer and Sundermeyer Chem. Ber. 1991, 124(11), 2405-2410, have previously reported a synthetic method to the compound H3Ge—SiH3. Their synthetic methodology, however, did not afford high enough yields for practical use as a CVD source for the synthesis of semiconductor systems.
It an object of the present invention to provide compounds that display the necessary physical and chemical properties to be viable precursors for chemical vapor deposition (CVD) of Si—Ge semiconductors and related group IV alloys.
It is still another object of the present invention to provide a method for synthesizing such compounds that utilizes high-yield single-step substitution reactions involving commercially available starting materials.
It is yet another object of the present invention to provide a method for synthesizing trisilane that utilizes high-yield single-step substitution reactions involving commercially available starting materials.
Additional objects and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations pointed out in the appended claims.